Ancillary ligand and olefin substituent effects on olefin dissociation for cationic zirconocene complexes bearing a coordinated pendant olefin

Article abstract of DOI:10.1021/om010363n

A series of zirconocene complexes bearing 2,2-dimethyl-2-sila-4-pentenyl substituents (and methyl-substituted olefin variants) ((η⁵-C₅H₅)₂Zr(CH₃)(CH ₂SiMe₂CH₂CR¹ =CR²R³) (R¹, R², R³ = H, CH₃, 1, 5-7), (η⁵-C₅H₄CMe₃)₂ Zr(CH₃) (CH₂SiMe₂CH₂ CH=CH₂) (2), {Me₂Si(η⁵-C₅ H₄)₂}Zr(CH₃) (CH₂SiMe₂ CH₂CH=CH₂) (3), and {1,2-(SiMe₂)₂(η⁵-C₅H₃ )₂Zr(CH₃) (CH₂SiMe₂CH₂CH=CH₂) (4)) have been prepared. Methide abstraction with B(C₆F₅)₃ results in reversible coordination of the tethered olefin to the cationic zirconium center. The kinetics of olefin dissociation have been examined using NMR methods, and the effects of ligand variation for unlinked, singly [SiMe₂]-linked, and doubly [SiMe₂]-linked bis(cyclopentadienyl) arrangements have been compared (ΔG? values for olefin dissociation vary from 11.4 to 15.6 kcal·mol^-1 measured over the temperature range 223-283 K). For the cation derived from 4 the kinetics for olefin dissociation and site epimerization (inversion at zirconium) can be distinguished. Additionally, with this ligand system competitive binding of the olefin and the [CH₃B(C₆F₅)₃] anion is observed. Methide abstraction from {1,2-(SiMe₂)₂(η⁵-C₅ H₃)₂}Zr(CH₃) (CH₂CMe₂CH₂CH=CH₂) results in rapid β-allyl elimination with loss of isobutene to cleanly afford the allyl cation [{1,2-(SiMe₂)₂(η⁵-C₅ H₃)₂}Zr (η³-CH₂CH=CH₂)]⁺.

Full text of DOI:10.1021/om010363n

Organometallics 2001, 20, 4253-4261
4253
An cilla r y Liga n d a n d Olefin Su bstitu en t Effects on
Olefin Dissocia tion for Ca tion ic Zir con ocen e Com p lexes
Bea r in g a Coor d in a ted P en d a n t Olefin
Christopher G. Brandow, Arjun Mendiratta, and J ohn E. Bercaw*
Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of
Technology, Pasadena, California 91125
Received May 4, 2001
A series of zirconocene complexes bearing 2,2-dimethyl-2-sila-4-pentenyl substituents (and
methyl-substituted olefin variants) ((η5-C5H5)2Zr(CH3)(CH2SiMe2CH2CR1dCR2R3) (R1, R2,
R3 ) H, CH3, 1, 5-7), (η5-C5H4CMe3)2Zr(CH3)(CH2SiMe2CH2CHdCH2) (2), {Me2Si(η5-C5H4)2}-
Zr(CH3)(CH2SiMe2CH2CHdCH2) (3), and {1,2-(SiMe2)2(η5-C5H3)2Zr(CH3)(CH2SiMe2CH2CHd
CH2) (4)) have been prepared. Methide abstraction with B(C6F5)3 results in reversible
coordination of the tethered olefin to the cationic zirconium center. The kinetics of olefin
dissociation have been examined using NMR methods, and the effects of ligand variation
for unlinked, singly [SiMe2]-linked, and doubly [SiMe2]-linked bis(cyclopentadienyl) arrange-
ments have been compared (∆Gq values for olefin dissociation vary from 11.4 to 15.6
kcal‚mol-1 measured over the temperature range 223-283 K). For the cation derived from
4 the kinetics for olefin dissociation and site epimerization (inversion at zirconium) can be
distinguished. Additionally, with this ligand system competitive binding of the olefin and
the [CH3B(C6F5)3] anion is observed. Methide abstraction from {1,2-(SiMe2)2(η5-C5H3)2}Zr-
(CH3)(CH2CMe2CH2CHdCH2) results in rapid â-allyl elimination with loss of isobutene to
cleanly afford the allyl cation [{1,2-(SiMe2)2(η5-C5H3)2}Zr(η3-CH2CHdCH2)]+.
In tr od u ction
Resu lts a n d Discu ssion
Ziegler-Natta polymerization catalysis is practiced
on an enormous scale with both heterogeneous and
homogeneous catalysts. Metallocene-based catalysts
have allowed a more careful study of the mechanism
than was possible with heterogeneous catalysts. In this
regard, model complexes have been designed to stabilize
intermediates that are transient under typical catalytic
conditions. For example, several research groups have
prepared cationic, d0 metal olefin complexes of such
catalyst systems by tethering an olefin to an alkoxy,
alkyl, or cyclopentadienyl ligand.1 We have employed
this strategy to examine factors affecting olefin binding
in cationic zirconocenes by constructing olefin complexes
with the general formula shown in Scheme 1.2 This
series spans a limited range of unlinked, singly linked,
and doubly linked bis(cyclopentadienyl) ligands as well
as methyl substitution of the coordinated olefin.
Syn th esis of P en ten yl a n d Hexen yl Iod id es a n d
Meth yl(4-p en ten yl)zir con ocen es. The syntheses of
both 4,4-dimethyl-5-iodo-4-sila-1-pentene and 2,4,4-tri-
methyl-5-iodo-4-sila-1-pentene were accomplished ac-
cording to literature precedent by the reaction of the
respective Grignard reagent with ClCH2Si(CH3)2Cl in
ethereal solvent, followed by reaction with NaI.3 On the
other hand, the preparations of the cis- and trans-5,5-
dimethyl-6-iodo-5-sila-2-hexenes were not as straight-
forward. In both cases the respective 2-butenyltrichlo-
rosilane was prepared according to literature methods.4
These were treated with 2 equiv of methylmagnesium
chloride to yield the respective 2-butenyldimethylchlo-
rosilane, followed by addition of BrCH2Li. BrCH2Li was
prepared in situ from the reaction of CH2Br2 with
n-BuLi in the presence of the silyl chloride at -78 °C.
Much lower yields were obtained if the silyl chloride was
added after the preparation of BrCH2Li. We note in
passing that this appears to be a novel use of this
reagent, which previously has been studied extensively
as a [CH2] homologation reagent with alkylcatechol
boranes5 and represents an improvement over current
methods for preparing halomethyl(trialkyl)silanes.6
(1) (a)Wu, Z.; J ordan, R. F.; Petersen, J . L. J . Am. Chem. Soc. 1995,
117, 5867. (b) Casey, C. P.; Hallenbeck, S. L.; Pollock, D. W.; Landis,
C. R. J . Am. Chem. Soc. 1995, 117, 9770. (c) Casey, C. P.; Hallenbeck.
S. L.; Wright, J . M.; Landis, C. R. J . Am. Chem. Soc. 1997, 119, 9681.
(d) Casey, C. P.; Fagan, M. A.; Hallenbeck, S. L. Organometallics 1998,
17, 287. (e) Galakhov, M. V.; Heinz, G.; Royo, P. J . Chem. Soc., Chem.
Commun. 1998. (f) Casey, C. P.; Carpenetti, D. W.; Sakuri, H. J . Am.
Chem. Soc. 1999, 121, 9483. (g) Casey, C. P.; Carpenetti, D. W.
Organometallics 2000, 19, 3970. (h) Carpentier, J .-F.; Wu, Z.; Lee, C.
W.; Stro¨mberg, S.; Christopher, J . N.; J ordan, R. F. J . Am. Chem. Soc.
2000, 122, 7750. (i) Carpentier, J .-F.; Maryin V. P.; Luci, J .; J ordan,
R. F. J . Am. Chem. Soc. 2001, 123, 898.
(3) Fleming, I.; Patel, S. K.; Urdi, C. J . J . Chem. Soc., Perkin Trans
1 1989, 115.
(4) Iseki, K.; Kuroki, Y.; Takahashi, M.; Satoshi, K.; Kobayashi, Y.
Tetrahedron 1997, 3513.
(5) Michnick, T. J .; Matteson, D. S. Synlett 1991, 631.
(6) Cunico, R. F.; Gill, H. S. Organometallics 1982, 1, 1.
(2) Information on cation 8 is presented in the accompanying
article: Casey, C. P.; Carpenetti, D. W., II; Sakurai, H. Organometallics
2001, 20, 4262.
10.1021/om010363n CCC: $20.00 © 2001 American Chemical Society
Publication on Web 09/05/2001

4254 Organometallics, Vol. 20, No. 20, 2001
Brandow et al.
Sch em e 1
Sch em e 2
After purification by column separation on silica gel, the
hexenyl bromide was treated with NaI to give the
hexenyl iodide.
The methyl(4-pentenyl)zirconocenes were generally
obtained as oils via treatment of the appropriate 4-pen-
tenyllithium reagent, generated in situ by lithium-
halogen exchange, with a methylchlorozirconocene
(Scheme 3).
P r ep a r a tion a n d Kin etic Stu d ies of Ca tion ic
P en d a n t Olefin Com p lexes. Abstraction of methide
from 1 with B(C6F5)3 at -78 °C results in the immediate
formation of 8 (eq 1).
(0.19, 2.55), (2) the protons on the terminal vinyl carbon
are separated 3.6 ppm (2.25, 5.87), (3) the proton on the
internal olefin carbon is at 8.6 ppm, 2 ppm downfield
from its position for 1. The first two features suggest
differing proton positions relative to the magnetic fields
resulting from cyclopentadienyl ring currents. The large
downfield shift for the proton of the internal vinylic
carbon has been suggested to result from resonance
structures with a positive charge on this carbon,1a,f
a
suggestion that is certainly supported by the very
downfield chemical shift for this proton of 8. The
presence of a â-silicon would further stabilize such a
resonance structure.7
When solutions of 8 are warmed, a dynamic process
ensues, which we attribute to olefin dissociation followed
by fast recoordination. The ∆Gq(248 K) ) 13.1 kcal‚mol-1
.
We have modeled the coalescence using GNMR line
shape analysis8 and determined that the activation
parameters for this process are ∆Hq ) 13.4 kcal‚mol-1
,
∆Sq ) 0.7 eu. The rates measured to determine the
activation parameters for most cases were obtained over
only 20-25 °C ranges. Thus, while our Eyring plots
have an excellent fit to the data, we do not have enough
confidence in activation parameters derived from this
limited temperature range to draw firm conclusions
from them. Hence, we are confident only to compare free
energies of activation, which appear to approximate the
corresponding enthalpies of activation in most cases,
since the activation entropies are near zero.
Several features in the 1H NMR spectrum (CD2Cl2, -78
°C) of static 8 are notable: (1) the two protons on the
R-carbon display a chemical shift difference of 2.3 ppm
(7) Lambert, J . B. Tetrahedron 1990, 46, 2677.
(8) gNMR, v. 3.6; Cherwell Scientific Publishing: Oxford, 1996.

Olefin Dissociation for Cationic Zr Complexes
Organometallics, Vol. 20, No. 20, 2001 4255
Sch em e 3
Sch em e 4
The possibility of a counteranion effect on the olefin
dissociation was considered, and use of an alternative,
less coordinating anion was attempted with [Ph3C]-
[B(C6F5)4] as a methide abstracting reagent. Unfortu-
nately, significant amounts (>80%) of what appears to
be the methyl-bridged dimeric cation, {[(η5-C5H5)2Zr-
(CH2SiMe2CH2CHdCH2)]2(µ2-CH3)}+, are formed when
stoichiometric amounts of [Ph3C][B(C6F5)4] are used.
Rates were measured for comparison by addition of 3
molar equiv of either [n-Bu4N]+[CH3B(C6F5)3]- or
[n-Bu4N]+[B(C6F5)4]- to CD2Cl2 solutions of 8, thus
holding the ionic strength constant. The resulting
variable-temperature 1H NMR spectra for these two
samples are indistinguishable from each other. We
conclude therefore that excess [CH3B(C6F5)3]- does not
significantly change the rate of olefin dissociation.
Solvent assistance has also been considered. The insta-
bility of 8 and its exceedingly high Lewis acidity restrict
the choice of solvent. Whereas the rate of olefin dis-
sociation in CD2Cl2 and C6D5Cl are the same within
experimental error, the similarity of these two solvents
leaves open the issue of solvent assistance in olefin
dissociation.
Upon activation with B(C6F5)3 there was no observed
change in the peak intensities of the protons at the
R-carbon or at the γ-carbon, which would be expected
for reversible insertion and ring opening of the resulting
cyclobutylmethylzirconocenium cation (Scheme 4), in-
dicating that no insertion is occurring.
We were surprised by the lack of observed insertion
and thus undertook a DFT calculation to estimate the
thermodynamics of the process. A comparison of the sila-
substituted cyclization to the all-carbon analogue indi-
cated that 1,1,3-trimethyl-1-silacyclobutane is 3 kcal‚
mol-1 higher in energy than 4,4-dimethyl-4-sila-1-
pentene, as compared to only 0.2 kcal‚mol-1 for the 4,4-
dimethyl-1-pentene to 1,1,3-trimethylcyclobutane con-
version.9 The calculated difference of only 2.8 kcal‚mol-1
would not seem to account for the very slow insertion
To determine whether reversible olefin insertion was
occurring, isotopically labeled complex 1 with deuterium
at the γ-carbon was prepared. Since the synthesis
utilizes a 1:1 mixture of CD2CHCH2MgBr and CH2-
CHCD2MgBr, the incorporation of deuterium was 50%
at the γ-carbon and 50% at the terminal olefin carbon.
(9) J aguar 3.5; Schrodinger, Inc.: Portland, Oregon, 1998.

4256 Organometallics, Vol. 20, No. 20, 2001
Brandow et al.
Sch em e 5
8-d2, considering the relatively facile insertion (∆Gq(248
K) ) 14.4 kcal‚mol-1) reported by Casey and co-workers
for (η5-C5Me5)2Y(CD2CMe2CH2CHdCH2).1c Higher tem-
peratures were not examined, because above -30 °C 8
begins to decompose irreversibly.
dissociation barrier for 14 to be less than for the parent
complex 8. Clearly this result is consistent with the
notion that positive charge builds up at the internal
olefin carbon: the electron-donating methyl stabilizes
the positive charge in resonance structure 14b.
Olefin Su bstitu en t Effects. To address the effects
of methyl substitution on olefin binding to d0 metals,
we sought to prepare olefins with a single methyl group
at each vinylic position. The cis-hexenyl complex 13 was
prepared by methide abstraction from 6 with B(C6F5)3
in CD2Cl2 at -78 °C. However, the major species in solu-
tion is the ion pair complex with only a small fraction
identified as the complex 13 having coordinated olefin.
This assignment is consistent with the proton spectra,
although not all of the peaks could be assigned, and the
fluorine NMR, which shows [C6F5] resonances corre-
sponding to both coordinated and free [CH3B(C6F5)3]-.
The barrier for olefin exchange was determined by NMR
simulation and was found to be 11.4 kcal‚mol-1 at 223
K, considerably lower than that of the parent complex
8. The trans-hexenyl complex 5 was similarly activated
and did, in fact, yield complex 12 with a coordinated
olefin and solvent-separated [CH3B(C6F5)3]- as the
major species. There also appears to be a small amount
of the anion coordinated species. The ratio of these two
species does not change over a wide variety of temper-
atures, and they do not appear to exchange with each
other on the NMR time scale at temperatures up to -30
° C. NMR simulation of the peak coalescence revealed
that the free energy of activation was 13.3 kcal‚mol-1
at 248 K for olefin dissociation, curiously essentially
unchanged from the parent pentenyl complex 8. Exam-
ining simple models of the cis- and trans-hexenyl
systems does lead one to predict greater steric repulsion
with olefin coordination for 13 vs 12; complex 13 has
the cis methyl directed toward a cyclopentadienyl
ligand. Perhaps most interesting is the relatively strong
olefin binding for 14 that results from methide abstrac-
tion from complex 7. The activation free energy for olefin
dissociation is measured to be 14.4 kcal‚mol-1 at 248
K, 1.3 kcal‚mol-1 greater than less crowded 8.10 On the
basis of sterics alone, we would expect the olefin
An cilla r y Liga n d Effects for Com p lexes Un -
lin k ed a n d Sin gly Lin k ed Zir con ocen iu m Olefin
Ca tion s. Cations 9 and 10 were prepared in a fashion
similar to 8, and the dynamic behavior was examined
by variable-temperature by NMR spectroscopy. The free
energies of activation for these complexes were also very
similar to that of 8: ∆Gq(248 K) ) 13.2 kcal‚mol-1 for
9; ∆Gq(248 K) ) 12.8 kcal‚mol-1 for 10. Despite the
presence of an ansa [SiMe2] linker or a sterically rather
demanding tert-butyl cyclopentadienyl substituent, the
olefin dissociation rates among the three metallocenium
cations are essentially the same. Significantly, for both
complexes 9 and 10, line shape analysis reveals that
site epimerization (inversion at Zr, Scheme 5) occurs
simultaneously with olefin dissociation.11
Dou bly Br idged a n sa -Metallocen iu m Cation Ole-
fin Com p lex. Despite the similarity of olefin dissocia-
tion barriers for complexes 8, 9, and 10, the fluxional
character of the doubly [SiMe2]-bridged complex 11 is
distinct. For complex 11, dynamic NMR behavior due
to olefin dissociation in CD2Cl2 is not apparent until 0
°C, as opposed to -55 °C for 8. The free energy of
activation for 11 (in C6D5Br, ∆Gq(283 K) ) 15.6
kcal‚mol-1) is more than 2 kcal‚mol-1 greater than for
8. Since the barriers for olefin dissociation are not
measurably different with [CH3B(C6F5)3]- or [B(C6F5)4]-
as counterion, it appears that the anion does not assist
in olefin dissociation. Additionally, at this temperature,
and even up to 75 °C, olefin dissociation and recoordi-
(10) This value for ∆Gq is extrapolated from activation parameters
(11) Although the symmetry for 8 does not allow measurement of
the site epimerization rate, we assume that inversion at zirconium
also accompanies olefin dissociation for this cation.
that were determined from an Eyring plot determined over a 30 °C
range; the free energy at 273 K is 14.8 kcal‚mol-1
.

Olefin Dissociation for Cationic Zr Complexes
Organometallics, Vol. 20, No. 20, 2001 4257
Sch em e 6
nation is not accompanied by site epimerization. It has
been observed for this type of doubly bridged zirconocene
complexes that the mechanism for ligand exchange is
dissociative, whereas unbridged zirconocenes exchange
ligands via an associative mechanism.12 In light of these
differences, it may be argued that olefin dissociation for
complexes 8, 9, and 10 involves solvent assistance,
whereas olefin facial exchange for complex 11 is entirely
dissociative. Exactly how these differences influence the
relative barriers for site epimerization are not clear (see
ref 12b).
Site epimerization for complex 11 cannot be observed
by NMR until 85 °C (∆Gq(358 K) ) 21.2 kcal‚mol-1) and
then only when 4 is activated with the [Ph3C][B(C6F5)4]
in C6D5Cl; all other combinations of solvent and activa-
tor that were attempted resulted in decomposition at
lower temperatures. This inversion at zirconium for 11
is not complicated by the presence of donor molecules,
coordinating anions, or (potentially agostic) â-hydro-
gens13 and allows us to place a lower limit on the barrier
for site epimerization of ca. 5.3 kcal‚mol-1 at 85 °C. The
height of this barrier provides some of the strongest
evidence to date of an inherent hindrance to site
epimerization for cationic zirconocenium alkyls, as
predicted by theoretical calculations.14
synthesized the neutral zirconocene methyl-2,2-di-
methyl-4-pentenyl complexes 16. In view of the reluc-
tance of the pendant sila-substituted pentenes to un-
dergo reversible olefin insertion, we prepared this
complex as a precursor to a cation that could serve as a
model for olefin insertion into a zirconium-carbon bond.
To our surprise, upon the addition of either B(C6F5)3 or
[Ph3C][B(C6F5)4] at -40 °C in C6D5Cl or C6D5Br only
allyl cation 18, resulting from rapid and clean â-allyl
elimination and loss of isobutene from the presumed
intermediate 17, was observed (Scheme 6).16 There was
no evidence of â-methyl elimination occurring. So far
as we are aware, this process represents the first
example of â-allyl elimination.
For this ligand system we can observe competitive
binding of the [CH3B(C6F5)3]- to the metal center in
C6D5Cl (eq 2).
The resulting cationic η3-allyl complex is fluxional,
and its dynamics have been examined by magnetization
transfer (∆Gq(275 K) ) 12. 4 kcal‚mol-1). The fluxional
process can be described as an η3 a η1 isomerization,
leading to stepwise interconversion of the syn and anti
methylene protons.
Con clu sion s
The equilibrium was examined between 0 and 65 ° C,
revealing the following thermodynamic parameters in
C6D5Cl: ∆H° ) 7.2 kcal‚mol-1 and ∆S° ) 22 e.u. Since
the equilibrium favors the formation of the coordinated
olefin complex at higher temperatures, despite two
species forming one, the separated ions must organize
the solvent significantly. The same species appears in
C6D5Br and CD2Cl2, but the equilibrium cannot be
measured accurately because it does not appear until
higher temperatures, just before decomposition sets in.15
Attem p ts to P r ep a r e a Dou bly Br id ged a n sa -
Meta llocen iu m Ca tion w ith a n All-Ca r bon P en -
d a n t Olefin : â-Allyl Elim in a tion . We have also
For this series of zirconocene alkyl cations with
pendant olefins, coordination of the CdC double bond
to zirconium is observed. Dynamic NMR behavior
indicates olefin dissociation and fast recoordination. The
binding of olefins with methyl substitution on the
terminal vinyl carbon appears to be influenced primarily
(15) Compound 11, when heated to higher temperatures, decom-
poses to give a halide-bridged dication dimer. This arises from metal-
halogen exchange with the bromobenzene solvent. After sitting over-
night in an NMR tube, crystals of this species grew. We determined
the structure of this species using X-ray crystallography, revealing it
to be a Zr(IV) bromide-bridged dimer [[{1,2-(SiMe2)2(η5-C5H3)2Zr]2(µ2-
Br)2][B(C6F5)4]2 (15) (see Supporting Information). Unfortunately, the
amount of 15 that was isolated precluded further study. The precise
mechanism of the reaction forming 15 is unknown at this time.
(16) The pentenyl complex, 17, can only be observed when 16 is
activated at -78 °C with [Ph3C][B(C6F5)4] in CD2Cl2. Although it is
not entirely pure, the diagnostic peaks in the 1H NMR spectrum of
the olefin complex can be observed: a multiplet at 8.4 ppm and a
matching set of doublets at -0.4 and 2.8 ppm. Upon warming to -50
°C, all peaks corresponding to 17 disappear, but the course of the
decomposition of the proposed olefin complex is not easily followed.
(12) (a) Wendt O.; Bercaw, J . E. Manuscript in preparation. (b)
Beck, S.; Lieber, S.; Schaper, F.; Geyer, A.; Brintzinger, H.-H. J . Am.
Chem. Soc. 2001, 123, 1483.
(13) (a) Deck, P. A.; Marks, T. J . J . Am. Chem. Soc. 1995, 117, 6128.
(b) Casey, C. P.; Fagan, M. A.; Hallenbeck, S. L. Organometallics 1998,
17, 287.
(14) Bierwagen, E. P.; Bercaw, J . E.; Goddard, W. A. J . Am. Chem.
Soc. 1994, 116, 1481.

4258 Organometallics, Vol. 20, No. 20, 2001
Brandow et al.
by measuring the peak separation of an ethylene glycol or
methanol standard before and after the experiments. Relax-
ation times (T1) for the resonances of interest were measured
at each temperature before the magnetization transfer experi-
ment using the inversion recovery method. Magnetization
transfer spectra were obtained by using a DANTE pulse
sequence.23 The data were fitted using the program CIFIT.24
by steric considerations, whereas methyl substitution
of the internal vinyl carbon appears to stabilize a
positive charge buildup, stabilizing the olefin complex.
Singly cyclopentadienyl-substituted and singly [SiMe2]-
linked zirconocenium cations have barriers for pendant
olefin dissociation that are essentially unchanged from
the parent bis(cyclopentadienyl) system. In the doubly
[SiMe2]-linked complex, olefin dissociation is much
faster than site epimerization, a process that involves
inversion at zirconium by moving the alkyl group. By
contrast, site epimerization is more rapid than olefin
dissociation for the other cations examined. We inter-
pret this difference as an indication that olefin dissocia-
tion in doubly linked metallocenes occurs by a dissocia-
tive mechanism, while olefin dissociation from the
unlinked and singly linked ansa-zirconocenes is solvent
assisted. The analogous, all-carbon tethered olefin could
not be isolated; isobutene is rapidly eliminated, and the
zirconocenium allyl cation is generated by facile â-allyl
elimination.
Sim p lified On e-P ot P r ep a r a tion of (C5H4)2(SiMe2)2. A
1 L Schlenk flask was purged with Ar, and 400 mL THF was
added via cannula transfer. Cyclopentadiene (20 g, 303 mmol)
was added. This mixture was cooled to 0 °C, and n-butyl-
lithium (189 mL, 303 mmol) was added by syringe, eventually
forming a white precipitate. This mixture was allowed to stir
for 1 h at room temperature. SiCl2Me2 (18.38 mL, 151 mmol)
was added dropwise by syringe to the solution at 0 °C over 10
min. This solution was allowed to warm to room temperature
and stir for 1 h. The butyllithium and SiCl2Me2 additions were
repeated one time. After the SiCl2Me2 addition, the solution
was allowed to warm to room temperature and stir overnight.
The solvent was then removed in vacuo, and 400 mL of
petroleum ether was added; the resulting slurry was stirred
and filtered at room temperature, then quickly attached to an
inert atmosphere filter frit and filtered. The remaining solid
was rinsed with an additional 150 mL of petroleum ether. The
solution was concentrated to ∼100 mL and cooled to 0° C for
1 h. The solid precipitate was filtered and rinsed twice with
cold petroleum ether. A colorless powder (15.3 g) was obtained
for an overall yield of 42%. The filtrate was collected and
placed in a freezer at -30° C, and more pure product was later
recovered. 1H NMR (benzene-d6, 300 MHz) isomer 1: δ -0.44
(s, 6H, Si(CH3), 0.37 (s, 6H, Si(CH3), 3.44 (s, 2H, SiCH), 6.64
(m, 6H, CpH), 6.94 (m, 2H, CpH); isomer 2: δ -1.23 (s, 3H,
Si(CH3), 0.21 (s, 3H, Si(CH3), 0.32 (s, 3H, Si(CH3), 0.44 (s, 3H,
Si(CH3), 3.54 (s, 2H, SiCH), 6.64 (m, 6H, CpH), 6.82 (m, 2H,
CpH).
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All reactions were carried out
using standard Schlenk techniques or in an inert atmosphere
1
glovebox. H, 13C, and 19F NMR spectra were obtained using
a Varian Inova500 or Varian Inova 300 MHz spectrometer.
All NMR solvents were distilled from CaH2. (η5-C5H5)2Zr(CH3)-
(Cl),17 {Me2Si(η5-C5H4)2}Zr(CH3)(Cl),18 B(C6F5)3,19 [Ph3C]-
[B(C6F5)4],20 {1,2-(SiMe2)2(η5-C5H3)2Zr(CH3)Cl,21 trans-Cl3-
SiCH2CHCHCH3,3 cis-Cl3SiCH2CHCHCH3,3 and CH2CHCD2-
MgBr22 were prepared according to literature procedures. All
solvents were dried on columns of anhydrous alumina and
molecular sieves (4 Å). Reagents were purchased from Aldrich
Chemical and were used as received.
Lin e Sh a p e Sim u la tion Exp er im en ts. Line shape analy-
ses of dynamic 1H spectra were carried out on a Varian Inova
500 MHz spectrometer. Reaction temperatures were deter-
mined by measuring the peak separation of an ethylene glycol
or methanol standard before or after the experiments. The
program gNMR was used to simulate the NMR spectra.8 To
simulate the olefin dissociation and recoordination to the
opposite face, the signals from either the diastereotopic cyclo-
pentadienyl protons, R-protons, or γ-protons were studied.
Specifically, the peaks for the diastereotopic protons of the
cyclopentadienyl rings were simulated for 8; the allylic protons
were simulated for 9; the allylic protons were simulated for
10; the R-protons were simulated for 12; the R-protons were
simulated for complex 13; and the R-protons were simulated
for complex 14. An example of the line shape analysis is given
in the Supporting Information section. The rate of site epimer-
ization for complexes 9, 10, and 11 was determined by
examining the coalescence of peaks due to diastereotopic
protons of the cyclopentadienyl ligands, as well as the peaks
corresponding to dimethylsilyl groups that bridge cyclopenta-
dienyl ligands.
4,4-Dim eth yl-5-iod o-4-sila -1-p en ten e. Allylmagnesium
bromide (67.5 mL, 2 M in THF) was added dropwise to a 500
mL ether solution of chloro(chloromethyl)dimethylsilane (19.2
g, 135 mmol) at 0 °C over 1 h. This mixture was allowed to
warm to room temperature and stir overnight. The product
was carefully quenched with 100 mL of H2O. The organic layer
was rinsed 3 times with 100 mL of H2O and once with 100
mL of brine. The crude oil was dissolved in 125 mL of dry
acetone, NaI (40 g, 266 mmol) was added, and the mixture
was stirred for 18 h. This mixture was taken up in 100 mL of
pentane and 100 mL of H2O. The organic layer was washed
with an additional 100 mL of H2O. The solvent was removed
by rotary evaporation, and the oil was distilled at 68-74 °C/
10 mmHg. A colorless oil (15.6 g) was collected for a 48% yield.
1H NMR (CDCl3, 300 MHz): δ 0.16 (s, 6H, Si(CH3)2), 1.66 (d,
2H SiCH2CH, J HH ) 7.2 Hz), 2.01 (s, 2H, ICH2Si), 4.9 (m, 2H,
SiCH2CHCH2), 5.78 (m, 1H, SiCH2CH). Anal. Calcd for C6H11
-
SiI: C, 30.01; H, 5.46. Found: C, 30.21; H, 5.45.
2,4,4-Tr im eth yl-5-iod o-4-sila -1-p en ten e. This compound
was prepared analogously to 4,4-dimethyl-5-iodo-4-sila-1-pen-
tene using CH2C(CH3)CH2MgCl in place of allylmagnesium
bromide. The final product was distilled at 95 °C/25 mmHg
and was isolated in 32% overall yield. 1H NMR (CDCl3, 300
MHz): δ 0.19(s, 6H, Si(CH3)2), 1.62 (s, 2H, SiCH2CCH3), 1.70
(s, 3H, CCH3), 2.05 (s, 2H, ICH2Si), 4.55 (s, 1H, CHHCCH3(CH2-
Ma gn etiza tion Tr a n sfer Exp er im en ts. Magnetization
transfer experiments were carried out on a Varian Unity+ 500
MHz spectrometer. Reaction temperatures were determined
Si)), 4.65 (s, 1H, CHHCCH3(CH2Si)). Anal. Calcd for C7H13
-
SiI:C, 33.08; H, 5.95. Found: C, 33.21; H, 5.91.
(17) Coutuier, S.; Gautheron, B. J . Organomet. Chem. 1978, 157,
C61.
(18) Bajgur, C. S.; Tikkanen, W. R.; Peterson, J . L. Inorg. Chem.
1985, 24, 2539.
(19) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2, 245
(20) Chien, J . C. W.; Tsai, W.-M.; Rausch, M. D. J . Am. Chem. Soc.
1991, 113, 8570.
5,5-Dim eth yl-6-iod o-5-sila -cis-2-h exen e. A solution of cis-
Cl3SiCH2CHCHCH3 (27.15 g, 143.3 mmol), prepared according
to literature procedure, in 1 L of diethyl ether was cooled to 0
°C. Methylmagnesium chloride (95.5 mL, 3 M, 286.6 mmol)
(21) Cano, A.; Cuenca, T.; Go´mez-Sal, P.; Manzanero, A.; Royo, P.
J . Organomet. Chem. 1996, 526, 227.
(22) Hill E. A.; Boyd, W. A.; Desai, H.; Darki, A.; Bivens, L. J .
Organomet. Chem. 1996, 514, 1.
(23) Morris, G. A.; Freeman, R. J . Magn. Reson. 1978, 29, 433-
462.
(24) Bain, A. D.; Cramer, J . A. J . Magn. Reson. 1996, 118A, 21-
27.

Olefin Dissociation for Cationic Zr Complexes
Organometallics, Vol. 20, No. 20, 2001 4259
was added over the course of 1 h. The volatiles were removed
by distillation under Ar, and three fractions were obtained with
varying amounts of methylated products. The first two frac-
tions were collected from 95 to 107 °C. Over the course of 15
min, n-butyllithium (26.6 mL, 1.6 M, 42.5 mmol) was added
along the walls of the flask cooled to -78 °C to a 100 mL THF
solution of CH2Br2 (2.97 mL, 42.5 mmol) and the mixture of
cis-butenylsilyl chloride. This mixture was allowed to stir at
-78 °C for an additional 15 min and then allowed to warm
and stir at room temperature for 20 min. A 20 mL portion of
pentane was added, the organic solution was rinsed repeatedly
with H2O, and the volatiles were dried over MgSO4. The
1H, SiCH2CHCH2). 13C (benzene-d6, 125.70 MHz): δ 1.0, 28.5,
28.6, 44.8, 110.2, 112.1, 136.6.
(η5-C5H4CMe3)2Zr (CH3)(CH2SiMe2CH2CHdCH2) (2). 1H
NMR (benzene-d6, 499.85 MHz): δ -0.01 (s, 3H, ZrCH3), 0.13
(s, 6H, ZrCH2Si(CH3)2), 0.11 (s, 2H, ZrCH2Si), 1.13 (s, 18H,
C(CH3)3), 1.58 (d, 2H, SiCH2CH, J HH ) 8.2 Hz), 5.0 (m, 2H,
SiCH2CHCH2), 5.50 (q, 2H, CpH, J HH ) 2.4 Hz), 5.60 (q, 2H,
CpH, J HH ) 2.4 Hz), 5.92 (q, 2H, CpH, J HH ) 2.4 Hz), 5.95 (m,
1H, SiCH2CH), 6.16 (q, 2H, CpH, J HH ) 2.4 Hz). 13C (benzene-
d6, 125.70 MHz): δ 0.8, 28.6, 30.9, 31.7, 32.9, 41.1, 106.7, 107.7,
108.2, 109.3, 111.1, 112.0, 138.9.
{(SiMe2)2(η5-C5H3)2}Zr (CH3)(CH2SiMe2CH2CHdCH2) (4).
1H NMR (benzene-d6, 499.85 MHz): δ -0.19 (s, 3H, ZrCH3),
-0.05 (s, 3H, Cp2Si(CH3)(CH3)), 0.07 (s, 5H, Cp2Si(CH3)(CH3),
ZrCH2), 0.14 (s, 6H, ZrCH2Si(CH3)2), 0.44 (s, 6H, (Si(CH3)-
(CH3))2), 1.57 (d, 2H, SiCH2CHCH2, J HH ) 8.1 Hz), 5.0 (m, 2H,
SiCH2CHCH2), 5.95 (m, 1H, SiCH2CH), 6.31 (t, 2H, CpH, J HH
) 2.7), 6.59 (m, 4H, CpH). 13C (benzene-d6, 125.70 MHz): δ
-4.8, -3.9, 0.4, 2.4, 2.5, 28.3, 29.9, 33.2, 110.2, 112.1, 113.0,
113.1, 134.2, 136.7.
(η5-C5H5)2Zr (CH3)(tr a n s-CH2SiMe2CH2CHdCHCH3) (5).
1H NMR (benzene-d6, 499.85 MHz): δ -0.17 (s, 3H, ZrCH3),
0.06 (s, 6H, Si(CH3)2), 0.09 (s, 2H, ZrCH2Si), 1.46 (d of qt, 2H,
SiCH2CHCH, J HH ) 7.8, 1.3 Hz), 1.70 (d of q, 3H, CHCHCH3,
J HH ) 6.3, 1.4 Hz), 5.36 (m, 1H, CHCHCH3), 5.54 (s, 1H,
CHCHCH3), 5.72 (s, 10H, CpH). 13C (benzene-d6, 125.70
MHz): δ 1.2, 18.3, 26.4, 28.4, 45.6, 110.2, 122.6, 128.8.
(η5-C5H5)2Zr (CH3)(cis-CH2SiMe2CH2CHdCHCH3) (6). 1H
NMR (benzene-d6, 499.85 MHz): δ -0.19 (s, 3H, ZrCH3), 0.05
(s, 6H, Si(CH3)2), 0.09 (s, 2H, ZrCH2Si), 1.50 (d, 2H, SiCH2-
CHCH), 1.62 (d, 3H, CHCHCH3), 5.47 (m, 1H, CHCHCH3),
5.63 (s, 1H, CHCHCH3), 5.75 (s, 10H, CpH). 13C (CD2Cl2,
125.70 MHz): δ 2.8, 14.6, 23.4, 29.5, 47.9, 112.2, 122.3, 129.8.
13C NMR spectra was taken in CD2Cl2 in order to identify a
resonance that was obscured in benzene-d6.
product was purified by column chromatography with
a
pentane eluant. The oil was distilled at 75-80 °C/18 Torr for
further purification. The oil and NaI (3 g, 20 mmol) were added
to 25 mL of dry acetone and stirred for 24 h. The mixture was
added to 100 mL of pentane, rinsed four times with 50 mL of
H2O, and then dried over MgSO4. The volatiles were removed
by rotary evaporation, and the resulting oil was obtained in
9.1% yield. 1H NMR (CDCl3, 300 MHz): δ 0.17 (s, 6H,
Si(CH3)2)), 1.58 (d, 3H, CHCH3), 1.63 (d, 2H, CH2CH), 2.02 (s,
2H, ICH2Si), 5.4 (m, 2H, CH2CHCHCH3). Anal. Calcd for
C7H13SiI: C, 33.08; H, 5.95. Found: C, 33.60; H, 6.0.
5,5-Dim eth yl-6-iod o-5-sila -tr a n s-2-h exen e. Starting with
trans-Cl3SiCH2CHCHCH3, which is prepared according to
literature procedure, the preparation of this compound is
identical to that of 5,5-dimethyl-6-iodo-5-sila-cis-2-hexene. 1H
NMR (CDCl3, 300 MHz): δ 0.14 (s, 6H, Si(CH3)2), 1.56 (d, 2H,
CH2CH), 1.63 (d, 3H, CHCH3), 2.0 (s, 2H, ICH2Si), 5.35 (m,
2H, CH2CHCHCH3). Anal. Calcd for C7H13SiI: C, 33.08; H,
5.95. Found: C, 34.07; H, 6.09.
3,3-Dideu ter o-4,4-dim eth yl-5-iodo-4-sila-1-pen ten e. This
compound was prepared analogously to 4,4-dimethyl-5-iodo-
4-sila-1-pentene using CH2CHCD2MgBr (and CD2CHCH2-
MgBr), which is prepared according to literature procedure.
1H NMR (CDCl3, 300 MHz): δ 0.19(s, 6H, Si(CH3)2), 1.62 (d,
1H, SiCH2CH), 2.0 (s, 2H, ICH2Si), 4.85 (m, 1H, CH2CH(CH2-
Si)), 5.7 (m, 1H, CH2CH(CH2Si)). Anal. Calcd for C6H9D2SiI:
C, 29.76; H, 5.45. Found: C, 29.82; H 5.51.
(η5-C5H5)2Zr (CH3)(CH2SiMe2CH2C(CH3)dCH2) (7). 1H
NMR (benzene-d6, 499.85 MHz): δ -0.11 (s, 3H, ZrCH3), 0.19
(s, 6H, Si(CH3)2), 0.2 (s, 2H, ZrCH2Si), 1.62 (s, 2H, SiCH2-
CCH3), 1.80 (s, 3H, CCH3), 4.70 (s, 1H, SiCH2C(CH3)CHH),
4.80 (s, 1H, SiCH2C(CH3)CHH), 5.75 (s, 10H, CpH). 13C
(benzene-d6, 125.70 MHz): δ 1.7, 25.6, 28.6, 32.4, 45.3, 107.9,
110.2, 144.7.
Gen er a l P r oced u r e for P r ep a r a tion of Zir con ocen e
Meth ylp en ten yl Com p lexes (1, 2, 4-7). A 25 mL Schlenk
flask with a rubber septum was purged with N2 for 10 min. A
10 mL portion of a degassed 3:2 mixture of petroleum ether
and diethyl ether was added by syringe. To this mixture was
added 4,4-dimethyl-5-iodo-4-sila-1-pentene (240 mg, 1.0 mmol)
by syringe. This mixture was cooled to -78 °C, and tert-
butyllithium (1.18 mL, 2.0 mmol) was added dropwise by
syringe over 7 min and stirred for 20 min at -78 °C. A toluene
solution containing Cp2Zr(CH3)(Cl) (300 mg, 1.1 mmol) was
added by syringe in <1 min, the mixture was stirred for 5 min
at -78 °C, and then allowed to warm slowly to 0 °C over the
course of 2 h. The solvent was removed in vacuo. The flask
was filled with argon, quickly attached to a swivel frit
assembly, and evacuated. A 10 mL sample of petroleum ether
was vacuum transferred onto the solid stirred at room tem-
perature and then filtered. The remaining solid was rinsed
once, and the petroleum ether was removed in vacuo, leaving
behind a yellow oil, which was left under vacuum for 30 min
to remove residual solvent.
(η5-C5H5)2Zr (CH3)(CH2SiMe2CH2CHdCH2) (1). 1H NMR
(benzene-d6, 499.85 MHz): δ -0.17 (s, 3H, ZrCH3), 0.04 (s,
6H, Si(CH3)2), 0.05 (s, 2H, ZrCH2Si), 1.50 (d of t, 2H, SiCH2-
CHCH2, J HH ) 8.2, 1.1 Hz), 4.90 (m, 2H, SiCH2CHCH2), 5.71
(s, 10H, CpH), 5.73 (s, 1H, SiCH2CHCH2). 13C (benzene-d6,
125.70 MHz): δ 1.0, 28.5, 28.6, 44.8, 110.2, 112.1, 136.6.
(η5-C5H5)2Zr (CH3)(CH2SiMe2CD2CHdCH2)/(η5-C5H5)2Zr -
(CH3)(CH2SiMe2CH2CHdCD2) (1-d 2). 1H NMR (benzene-d6,
499.85 MHz): δ -0.17 (s, 3H, ZrCH3), 0.04 (s, 6H, Si(CH3)2),
0.05 (s, 2H, ZrCH2Si), 1.50 (d, 1H, SiCH2CHCD2, J HH ) 8.2
Hz), 4.90 (m, 1H, SiCD2CHCH2), 5.71 (s, 10H, CpH), 5.73 (s,
{(SiMe2)2(η5-C5H3)2}Zr (CH3)(CH2CMe2CH2CHdCH2) (15).
1H NMR (benzene-d6, 300 MHz): δ -0.61 (s, 3H, ZrCH3), 0.10
(s, 3H, Si(CH3)), 0.12 (s, 3H, Si(CH3)), 0.45 (s, 6H, (Si(CH3)-
(CH3))2), 0.62 (s, 2H, ZrCH2Si(CH3)2), 0.97 (s, 6H, ZrCH2C-
(CH3)2), 2.00 (d, 2H, C(CH3)2CH2CHCH2, J HH ) 7.5 Hz), 5.07
(m, 2H, C(CH3)2CH2CHCH2), 5.90 (m, 1H, C(CH3)2CH2CH),
6.32 (t, 2H, CpH, J HH ) 2.1), 6.59 (s, 2H, CpH), 6.67 (s, 2H,
CpH). 13C (benzene-d6, 75.4 MHz): δ -4.5, -3.6, 2.6, 2.8, 28.6,
31.8, 37.5, 52.5, 69.2, 110.2, 112.6, 113.3, 116.1, 137.3.
{Me2Si(η5-C5H4)2}Zr (CH3)(CH2SiMe2CH2CHdCH2) (3).
A solution of 4-sila-1-pentenylmagnesium iodide in THF (3.94
mL, 2.87 mmol) was added against an Ar counterflow to a 120
mL methylene chloride solution of Me2SiCp2ZrCl2 (1.0 g, 2.87
mmol) in a 250 mL Schlenk flask at 0 °C. This mixture was
allowed to warm to room temperature and stirred overnight.
The solvent was removed, and benzene was condensed onto
the residue and warmed to room temperature. This solids were
filtered away, and the solvent was removed from filtrate to
afford a solid, which included 5-10% of the bis(pentenyl) and
5-10% of the dichloro complexes and was rinsed two times
with petroleum ether. This solid (0.67 g, 1.56 mmol) was
dissolved in diethyl ether at -78 °C, and a diethyl ether
solution of methyllithium (1.55 mL, 2.34 mmol) was added
dropwise. This mixture was stirred at -78 °C for 1 h and then
was warmed to room temperature for 1 h. The volatiles were
removed, and petroleum ether was condensed onto the solid.
After filtration the solvent was removed in vacuo, leaving a
yellow oil behind. 1H NMR (benzene-d6, 499.85 MHz): δ -0.06
(s, 3H, ZrCH3), 0.07 (s, 3H, Cp2Si(CH3)(CH3)), 0.10 (s, 6H,

4260 Organometallics, Vol. 20, No. 20, 2001
Brandow et al.
ZrCH2Si(CH3)2), 0.11 (s, 2H, ZrCH2Si), 0.13 (s, 3H, Cp2Si(CH3)-
(CH3)), 1.55 (d of t, 2H, SiCH2CHCH2), 5.00 (s, 2H, SiCH2-
CHCH2, 5.41 (q, 2H, CpH), 5.53 (q, 2H, CpH), 6.53 (q, 2H,
CpH), 6.89 (q, 2H, CpH). 13C (benzene-d6, 125.70 MHz): δ -5.9,
-5.3, 0.8, 28.5, 29.0, 44.8, 102.4, 110.4, 112.1, 114.0, 120.0,
120.6, 136.65.
Gen er a l P r oced u r e for Meth id e Abstr a ction fr om th e
Meth yla lk en yl Zir con ocen es. Because the alkenyl com-
plexes are typically an oil, calibrated solutions in either CD2-
Cl2 or C6D5Cl were prepared. In an inert atmosphere glovebox,
B(C6F5)3 (20 mg, 39.1 µmol) was weighed out in a screw-capped
NMR tube with a Teflon septum. A 0.7 mL sample of NMR
solvent was added, and the septum cap was screwed on. The
zirconocene solution (60 µL, 0.5 M, 30 µmol) was measured in
a syringe. Outside of the glovebox, the walls of the NMR tube
were cooled to -78 °C, and then the zirconocene solution was
added by syringe to the sealed NMR tube and the contents
were carefully shaken, keeping the solution cold. The NMR
solution immediately became bright yellow.
7.52 (s, 1H, CpH). 13C NMR (CD2Cl2, 125.70 MHz, -80 °C): δ
-5.5, -5.4, 1.2, 1.4, 10.0, 32.6, 52.0, 100.1, 104.5, 107.6, 113.4,
114.1, 118.3, 118.8, 121.1, 123.6, 125.0, 128.4, 136.5 (d, J CF
)
240 Hz), 137.9 (d, J CF ) 242 Hz), 142.3 (d, J CF ) 238 Hz), 168.1.
19F NMR (CD2Cl2, 470.25 MHz, -80 °C): δ -168.4 (t, 6F, J FF
) 20 Hz), -162.2 (t, 3F, J FF ) 21 Hz), -135.1 (d, 6F, J FF ) 21
Hz).
[{(SiMe2)2(η5-C5H3)2}Zr (CH2SiMe2CH2CHdCH2)][MeB-
(C6F 5)3] (11-MeBAr F ). 1H NMR (C6D5Cl, 499.85 MHz, -40
°C): δ -0.09 (d, 1H, ZrCHH, J HH ) 13.5 Hz), -0.05 (s, 3H,
Cp2Si(CH3)(CH3)), 0.02 (s, 3H, ZrCH2Si(CH3)(CH3)), 0.05 (s,
3H, Cp2Si(CH3)(CH3)), 0.31 (s, 3H, ZrCH2Si(CH3)(CH3)), 0.66
(s, 6H, Cp2(Si(CH3)(CH3))2), 1.44 (s, 3H, BCH3), 1.74 (1H, d of
d, SiCHHCHCH2, J HH ) 8.4, 12.3 Hz), 1.88 (m, 1H, SiHH-
CHCH2), 1.96 (d, 1H, ZrCHH, J HH ) 13.5 Hz), 1.97 (m, 1H,
SiCH2CHCHH), 5.49 (d of d, 1H, SiCH2CHCHH, J HH ) 2.9,
17 Hz), 6.10 (s, 1H, CpH), 6.15 (s, 1H, CpH), 6.57 (s, 1H, CpH),
6.64 (s, 1H, CpH), 6.92 (s, 1H, CpH), 6.97 (s, 1H, CpH), 8.08
(m, 1H, SiCH2CHCH2). 13C NMR (C6D5Cl, 125.70 MHz, -40
°C): δ -5.0, 4.2, 0.1, 1.2, 1.9, 2.1, 33.4, 46.9, 98.9, 115.1, 117.4,
117.5, 117.9, 118.0, 136.0, 137.1 (d, J CF ) 233 Hz), 137.8 (d,
J CF ) 241 Hz), 148.9 (d, J CF ) 253 Hz), 170.1. 19F NMR (CD2-
Cl2, 470.25 MHz, -40 °C): δ -167.7 (t, 6F, J FF ) 23 Hz),
-165.1 (t, 3F, J FF ) 21 Hz), -135.0 (d, 6F, J FF ) 21 Hz).
[{(SiMe2)2(η5-C5H3)2}Zr(CH2SiMe2CH2CHdCH2)][B(C6F5)4]
(11-BAr F 4). 1H NMR (C6D5Cl, 499.85 MHz, -40 °C): δ -0.08
(d, 1H, ZrCHH, J HH ) 13.5 Hz), -0.04 (s, 3H, Cp2Si(CH3)-
(CH3)), 0.03 (s, 3H, ZrCH2Si(CH3)(CH3)), 0.08 (s, 3H, Cp2Si-
(CH3)(CH3)), 0.33 (s, 3H, ZrCH2Si(CH3)(CH3)), 0.67 (s, 6H,
[(η5-C5H5)2Zr (CH2SiMe2CH2CHdCH2][MeB(C6F 5)3] (8).
1H NMR (CD2Cl2, 499.85 MHz, -80 °C): δ 0.06 (s, 3H, ZrCH2-
Si(CH3)(CH3)), 0.38 (d, 1H, ZrCHH, J HH ) 12.5 Hz), 0.42 (s,
3H, BCH3), 0.46 (s, 3H, ZrCH2Si(CH3)(CH3)), 2.01 (d of d, 1H,
SiCHHCH, J HH ) 11 Hz, 11 Hz), 2.12 (m, 1H, SiCHHCH), 2.34
(m, 1H, SiCH2CHCHH), 2.57 (d, 1H, ZrCHH, J HH ) 12.5 Hz),
5.92 (d, 1H, SiCH2CHCHH, J HH ) 17 Hz), 6.62 (s, 5H, CpH),
6.65 (s, 5H, CpH), 8.65 (m, 1H, SiCH2CH). 13C NMR (CD2Cl2,
125.70 MHz, -80 °C): δ 0.4 (q, Si(CH3)2, J C-H ) 119), 1.7 (q,
Si(CH3)2, J C-H ) 121), 9.8 (q, B-CH3, J C-H ) 124.3 Hz), 32.9
(t, ZrCH2, J C-H ) 128.7 Hz), 53.5 (t, SiCH2CHCH2, J C-H
113.6 Hz), 99.5 ppm (t, SiCH2CHCH2, J C-H ) 153 Hz), 113.9
(d of qt, C5H5, J C-H ) 167 Hz), 115.3 (d of qt, C5H5, J C-H
)
Cp2(Si(CH3)(CH3))2), 1.75 (1H, d of d, SiCHHCHCH2, J HH )
8.4, 12.3 Hz), 1.92 (m, 1H, SiHHCHCH2), 1.97 (d, 1H, ZrCHH,
J HH ) 13.5 Hz), 1.99 (m, 1H, SiCH2CHCHH), 2.15 (s, 3H, Ph3-
CCH3), 5.49 (d of d, 1H, SiCH2CHCHH, J HH ) 2.9, 17 Hz),
6.09 (s, 1H, CpH), 6.16 (s, 1H, CpH), 6.59 (s, 1H, CpH), 6.67
(s, 1H, CpH), 6.92 (s, 1H, CpH), 6.98 (s, 1H, CpH), 8.10 (m,
1H, SiCH2CHCH2). 13C NMR (C6D5Cl, 125.70 MHz, -40 °C):
δ -5.0, 4.3, 0.1, 1.2, 1.9, 2.1, 30.6, 33.4, 46.9, 52.7, 98.8, 115.1,
117.5, 117.7, 117.9, 118.1, 170.2. 19F NMR (CD2Cl2, 470.25
MHz, -40 °C): δ -169.2 (s, 8F), -165.3 (t, 4F, J FF ) 21 Hz),
-136.0 (s, 8F).
)
167 Hz), 128.1 (s, B-C), 136.0 (d, C-F, J CF)247 Hz), 137.0
(d, C-F, J CF ) 244 Hz), 147.7 (d, C-F, J CF ) 246), 175.1 (d,
SiCH2CHCH2, J C-H ) 155 Hz). 19F NMR (CD2Cl2, 470.25 MHz,
-80 °C): δ -167.0 (s, 6F), -164.3 (s, 3F, J FF ) 21 Hz), -134.0
(s, 6F).
[(η5-C5H5)2Zr (CH2SiMe2CD2CHdCH2][MeB(C6F 5)3]/[(η5-
C5H5)2Zr (CH2SiMe2CH2CHdCD2][MeB(C6F 5)3] (8-d 2). 1H
NMR (CD2Cl2, 499.85 MHz, -80 °C): δ 0.02 (s, 3H, Si(CH3)-
(CH3)), 0.25 (d, 1H, ZrCHHSiCH2, J HH ) 13 Hz), 0.30 (d, 1H,
ZrCHHSiCD2, J HH ) 13 Hz), 0.36 (s, 3H, BCH3), 0.41 (s, 3H,
Si(CH3)(CH3)), 2.01 (d of d, 0.5H, SiCHHCH, J HH ) 11 Hz, 11
Hz), 2.12 (m, 0.5H, SiCHHCH), 2.34 (m, 0.5H, SiCH2CHCHH),
2.51 (d, 1H, ZrCHH, J HH ) 13 Hz), 5.92 (d, 0.5H, SiCH2-
CHCHH, J HH ) 17 Hz), 6.57 (s, 5H, CpH), 6.59 (s, 5H, CpH),
8.62 (m, 1H, SiCH2CH).
[(η5 -C 5 H 4 C M e 3 )2 Zr (C H 2 S i M e 2 C H 2 C H dC H 2 ][M e B -
(C6F 5)3] (9). 1H NMR (CD2Cl2, 499.85 MHz, -80 °C): δ -0.31
(d, 1H, ZrCHH, J HH ) 12.5 Hz), 0.04 (s, 3H, Si(CH3)2), 0.42 (s,
3H, BCH3), 0.52 (s, 3H, Si(CH3)2), 1.09 (s, 18H, CCH3), 2.04
(m, 2H, SiCH2CHCH2), 2.19 (t, 1H, Si 5.67CH2CHCH2), 2.60
(d, 1H, ZrCHH, J HH ) 12.5 Hz), 5.96 (s, 1H, CpH), 6.31 (s,
1H, CpH), 6.55 (s, 2H, CpH), 6.71 (s, 1H, CpH), 6.99 (s, 1H,
CpH), 7.11 (s, 2H, CpH), 8.81 (m, 1H, SiCH2CHCH2). 13C NMR
(CD2Cl2, 125.70 MHz, -80 °C): δ 1.0, 3.2, 10.0, 31.3, 31.3, 33.3,
33.8, 34.3, 52.0, 99.0, 108.0, 110.5, 110.6, 111.8, 112.5, 115.9,
[(η5-C5H 5)2Zr (tr a n s-CH 2SiMe2CH 2CH dCH CH 3][MeB-
(C6F 5)3] (12). Coordinated olefin complex: 1H NMR (CD2Cl2,
499.85 MHz, -80 °C): -0.32 (d, 1H, ZrCHH, J HH ) 13.5 Hz),
0.03 (s, 3H, Si(CH3)(CH3)), 0.25 (d, 3H, CHCHCH3, J HH ) 5.5
Hz), 0.42 (s, 3H, BCH3), 0.47 (s, 3H, Si(CH3)(CH3)), 1.76 (d of
d, 1H, SiCHHCHCH2, J HH ) 12 Hz, J HH ) 12 Hz), 1.85 (m,
1H, SiCHHCHCH), 2.09 (d, 1H, ZrCHH, J HH ) 13.5 Hz), 5.68
(m, 1H, CHCHCH3), 7.55 (m, 1H, SiCH2CHCH). 13C NMR
(CD2Cl2, 125.70 MHz, -80 °C): δ 0.7, 5.0, 9.5, 9.8 (BCH3), 30.0,
45.9, 99.8, 112.0, 113.7, 128.3, 136.8, 137.7, 148.1, 167.4. 19F
NMR (CD2Cl2, 470.25 MHz, -80 °C): δ -135.3 (d, J FF ) 20
Hz), -165.5 (t, J FF ) 19 Hz), -168.3 (t, J FF ) 19 Hz). Ion pair
complex: 19F NMR (CD2Cl2, 470.25, -80 °C): δ -166.4 (t, 6F,
J FF ) 19 Hz), -161.6 (t, 3F, J FF ) 20 Hz), -136.2 (d, 6F, J FF
) 20 Hz).
[(η5-C 5H 5)2Zr (ci s-C H 2S iMe 2C H 2C H dC H C H 3][Me B -
(C6F 5)3] (13). 1H NMR (CD2Cl2, 499.85 MHz, 499.85 MHz, -80
°C) coordinated anion: δ -0.05 (s, 6H, Si(CH3)2), 0.33 (s, 3H,
BCH3), 1.37 (d, 2H, SiCH2CHCH), 1.42 (d, 3H, CHCHCH3),
1.53 (s, 2H, ZrCH2), 5.37 (m, 2H, SiCH2CHCHCH3), 6.25 (s,
10H, CpH). 19F NMR (CD2Cl2, 282.15 MHz, -80 °C): δ -166.3
(t, J FF ) 23 Hz), -161.5 (t, J FF ) 23 Hz), -136.2 (d, J FF ) 23
Hz); coordinated olefin: δ -0.04 (s, shoulder on larger peak
from coordinated anion, SiCH3), 0.29 (s, 3H, SiCH3), 1.16 (d,
1H, ZrCHH, J HH ) 12.9 Hz), 1.90 (d, 3H, CHCH3, J HH ) 6.3
Hz), 2.93 (d, 1H, ZrCHH, J HH ) 12.9 Hz), 4.68 (m, 1H, CHCH3),
6.34 (s, 5H, CpH), 6.56 (s, 5H, CpH), 7.10 (m, 1H, CH2CH).
[(η5-C5H5)2Zr (CH2SiMe2CH2C(CH3)dCH2][MeB(C6F 5)3]
118.9, 119.7, 128.61, 135.6 (d, J CF ) 242 Hz), 137.5 (d, J CF
)
236 Hz), 145.0, 148.6(d, J CF ) 234 Hz), 179.7. 19F NMR (CD2-
Cl2, 470.25 MHz, -80 °C): δ -168.3 (t, 6F, J FF ) 21 Hz),
-165.6 (t, 3F, J FF ) 21 Hz), -135.2 (d, 6F, J FF ) 22 Hz).
[{Me2Si(η5-C5H4)2}Zr(CH2SiMe2CH2CHdCH2][MeB(C6F5)3]
1
(10). H NMR (CD2Cl2, 499.85 MHz, -80 °C): δ 0.06 (s, 3H,
ZrCH2Si(CH3)(CH3)), 0.36 (s, 3H, ZrCH2Si(CH3)(CH3)), 0.41 (s,
3H, BCH3), 0.66 (s, 3H, Cp2Si(CH3)(CH3)), 0.71 (s, 3H, Cp2Si-
(CH3)(CH3)), 0.88 (s, 1H, ZrCHHSi, J HH ) 13 Hz), 2.01 (d of d,
1H, SiCHHCHCH2, J HH ) 12.2 Hz), 2.18 (m, 1H, SiCHH-
CHCH2), 2.34 (d, 1H, ZrCHHSi, J HH ) 13 Hz), 2.74 (d, 1H,
SiCH2CHCHH, J HH ) 6.5), 5.78 (s, 2H, CpH), 5.80 (s, 1H,
1
(14). H NMR (CD2Cl2, 499.85 MHz, -80 °C): 0.11 (s, 3H, Si-
CpH), 5.82 (s, 1H, CpH), 5.99 (d, 1H, SiCH2CHCHH, J HH
17 Hz), 7.27 (s, 1H, CpH), 7.35 (s, 1H, CpH), 7.44 (s, 1H, CpH),
)
(CH3)(CH3)), 0.26 (d, 3H, CHCHCH3, J HH ) 5.5 Hz), 0.39 (s,
3H, BCH3), 0.41 (s, 3H, Si(CH3)(CH3)), 0.64 (d, 1H, ZrCHH,

Olefin Dissociation for Cationic Zr Complexes
Organometallics, Vol. 20, No. 20, 2001 4261
J HH ) 13.5 Hz), 2.05 (d, 1H, ZrCHH, J HH ) 13 Hz), 2.12 (d of
d, 1H, SiCHHCHCH, J HH ) 9 Hz, J HH ) 4 Hz), 2.24 (d, 1H,
SiCHHC(CH3)CH2, J HH ) 10 Hz), 2.52 (overlapping, 1H,
SiCH2C(CH3)CHH, J HH ) 6.5), 2.52 (s, 1H, SiCH2C(CH3)CHH,
J HH ) 6.5 Hz), 5.46 (d, 1H, CHCHCH3, J HH ) 5.5 Hz), 6.49 (s,
5H, CpH), 6.61 (s, 5H, CpH). 13C NMR (CD2Cl2, 125.70 MHz,
-80 °C): δ 1.8, 3.0, 10.1, 31.7, 39.2, 52.5, 90.9, 115.6, 116.1,
129.1, 136.3 (d, J CF ) 242 Hz), 137.9 (d, J CF ) 239 Hz), 148.0
(d, J CF ) 236 Hz). 19F NMR (CD2Cl2, 470.25 MHz, -80 °C): δ
-168.3 (t, J FF ) 19 Hz), -165.5 (t, J FF ) 19 Hz), -135.3 (d,
J FF ) 20 Hz).
(d, J CF ) 240 Hz), 138.2 (d, J CF ) 241 Hz), 149.1 (d, J FF )
231 Hz).
Ack n ow led gm en t. This work has been funded by
the USDOE Office of Basic Energy Sciences (Grant No.
DE-FG03-88ER13431). The authors thank Professor
Charles Casey and Donald Carpenetti for helpful dis-
cussions of their similar results and Mr. Lawrence
Henling for obtaining the X-ray crystal structure.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra for
compounds 1, 1-d 2, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 17,
and 18, together with those portions of the spectra for 14 that
were simultaed with gNMR; details of the X-ray crystal
structure determination for [[{1,2-(SiMe2)2(η5-C5H3)2Zr]2(µ2-
Br)2][B(C6F5)4]2 (15), including tables of crystal data, atomic
coordinates, bond distances and angles, and structure factors.
This material is available free of charge via the Internet at
http://pubs.acs.org.
[{(SiMe2)2(η5-C5H3)2}Zr(CH2CMe2CH2CHdCH2)][B(C6F5)4]
(18-MeBAr F 3). 1H NMR (C6D5Cl, 499.85 MHz, -50 °C): δ
-0.05 (s, 6H, SiCH3), 0.05 (s, 6H, SiCH3), 1.44 (s, 3H, BCH3),
2.71 (2H, d, CHH, J HH ) 7.5 Hz), 3.07 (2H, d, CHH, J HH
)
15.0 Hz), 5.83 (s, 1H, CpH), 5.88 (s, 1H, CpH), 5.97 (m, 1H,
CH2CHCH2 6.05 (s, 2H, CpH), 6.38 (s, 2H, CpH). 13C NMR
(CD2Cl2, 125.70 MHz, -80 °C): δ -4.6, 3.0, 10.9, 24.6, 69.3,
107.2, 107.8, 108.0, 108.2, 111.6, 132.8, 142.4, 135.5, 137.0
OM010363N